Australian utility assists with Wessex Water rehabilitation project

Australian utility Sydney Water has assisted UK water utility Wessex Water in prolonging the life of a sewer by 200 years.

After biogenic corrosion was discovered in the first 200 m of its 8 km Coastal Interceptor Sewer, Wessex Water commissioned Dr Ian Bateman, a leading networks consultant from Australia, to verify the effectiveness of calcium aluminate cement (CAC) and the product’s ability to resist high levels of sulphuric acid.

The 1.8 m diameter sewer, built between 1964 and 1971, serves a population of around 34,500 and receives a maximum flow rate of 650 L/s from two rising mains.

Little was known about CAC as a corrosion barrier in European sewerage systems; however, Sydney Water was known to have used the material for concrete protection for more than 15 years.

“We spent a lot of time researching it in collaboration with Sydney Water, and we’re the first water company in the UK to use this product to line a sewer,” said Wessex Water Critical Sewers Engineer Nathan Hand.

“CAC has the advantage of greater resistance to hydrogen sulphide attack, down to a pH of 3.5, and forms a gel layer on its surface.”

The £1 million (AU$1.79 million) project, which was due for completion at the end of May, has embraced new concepts and historic solutions.

“We used the latest 3D building information modelling technology to locate the sewer underground and managed to sink a shaft within 50mm of the side of the sewer,” said Mr Hand.

“We’re looking to remove some of the energy from the sewage and reduce the turbulence, as this is what releases the hydrogen sulphide gas and causes corrosion.

“To do this we’re using an energy dissipating vortex, using technology that was originally invented by the predecessors of Wessex Water, Bristol City Council, back in the 1950s.

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